Frequency and wave length sound changer



April 5, 1938. MGCURDY 2,113,055

FREQUENCY AND WAVE LENGTH SOUND CHANGER Filed May 17, 1937 Patented Apr. 5, 1938 UNITED STATES PATENT OFFICE FREQUENCY AND WAVE LENGTH SOUND CHANGER 1 Claim.

This invention is an apparatus for substantially changing the length and amplitude of sound waves.

It is an object of the invention to very materially reduce or eliminate the objectionable wave impulses set up by operation of various machines, especially such as the more powerful pressure fluid operated motors which almost continuously discharge exhaust gases under high amplitude to the atmosphere.

Particularly, an object is to substantially instantly break a sound wave into lesser waves as to amplitude and length so that the objection or noise and vibration reactions to the wave will be avoided.

Further, an object is to provide a sound wave changer of utmost simplicity, of low cost relative to its given installation; of freedom from backpressure reactions; and which is devoid of labyrinthic characteristics and therefore will not choke up.

It is understood that the uses of the apparatus are very numerous and greatly varied, and it is not here intend-ed that the device is limited in O respect to its utility.

It is an object to provide a sound wave changer which will function to break a sound wave into any suitable number of lesser waves which will impact the atmosphere is such a reduced manner as to be incapable of undesired noise and reaction vibrations. At the same time it is an object to provide for such a subdivision of a wave without the use of very objectionable, closed type cushioning chambers and merely circuitous pas- 5 sages offering frictional resistance to the flow of exhausting gases.

The invention consists of certain advancements in this art as set forth in the ensuing disclosure and having, with the above, additional objects and advantages as hereinafter developed, and whose construction, combination and details of means and the manner of operation will be made manifest in the description of the annexed illustrative embodiment; it being understood that modifications, variations and adaptations may be resorted to within the scope, principle and spirit of the invention as it is more directly claimed in the appendage.

Figure 1 is an axial, elevational section.

Figure 2 is a cross-section on line 22 of Fig. 1.

Figure 3 is a schematic diagram of the stream flow and subdivision in the device.

In the adaptation of the Wave changer to an internal combustion motor the exhaust gases therefrom pass through a conduit 2 which is fixed concentrically in an end head 3 of a first stage chamber or cylinder 3 of a diameter of greater dimension than that of the conduit 2 at its connection with the head 3 which is the intake of the chamber 3.

The chamber 3 has a far end wall in the form of a flat annulus 4 against which is abutted a second stage chamber or cylinder 5 here shown as of less diameter than chamber 3 but larger than the concentric opening 4 of the wall or partition 4 and which is here plainly shown as. materially smaller than the inlet opening 3" in the intake head 3. Thus the wall 4 presents a very considerable face area 4 Fig. 2, across the projected bore of conduit 2 at the intake opening 3". This is clearly depicted in Fig. 3.

The far end of the second stage chamber 5 is provided with an end wall in the. form of a flat annulus 3 having an axial opening 6 materially smaller than the coaxial opening 4 of wall t so that it presents a considerable annular face area 6 concentric, in end view, of the face 4* of the wall 4.

The wall 6 is abutted by a third stage chamber or cylinder 1 of substantially larger diameter than the opening 6 of wall 6; chamber 1 having an imperforate end closure 8. A protective balile 9 is, if desired, fixed inwardly of the end closure 8.

It is understood that the number of stage chambers and their dimensions will be determined in accordance with given wave of sound to be subdivided.

Each chamber 3, 5 and l is provided with suitably disposed exhaust ports H], which, if so desired, according to the case, may be provided with external deflectors l l of any desired type, having the supplemental function of further altering the character of wave force discharging at the ports it). These ports are preferably so disposed as to provide for radial expansion of the gases in their respective stage chambers; particularly the arrested fractions of the gas stream stopped by the interposed barrier face areas 4 6 and 9.

The rigidly, coaxially joined chambers 3, 5 and l are preferably enclosed in a considerably larger collecting drum or shell 12 having an exhaust pipe l3 leading freely to an atmospheric discharge or outlet so that no objectionable backpressure is set up against gas discharged at the vent ports ID of the multi-stage wave changer formed of the several chambers 3, 5 and 1. It is understood that the gases and propagated sound waves are not caused by the shell I2 to be confined thereinand passed back to flow circuitously from one chamber to the other but are caused to pass directly to atmosphere, unless passed to some heat exchange apparatus for utilization of the contained heat.

Referring now to Fig. 3, it will be seen that a stream of exhaust gas will pass from the conduit 2 axially into chamber 3 where a peripheral, annular fraction of the cylindrical stream will abut the interposed annular area 4 of the transverse first stage wall 4. The arrested tubular stream S will then expand into the larger cylinder 3 at the space V and discharge through the ports Ill of chamber 3.

At the same instant a concentric tube S (or fraction) of the axially flowing gas stream has advanced to the stop area B of the wall 6 of second cylinder or chamber 5 and the arrested stream tube S expands to the annular space V in chamber 5 and escapes at ports l0.

Meantime the central stream fraction S axially fiows through hole 6 of wall 6 and abuts bafile 9 and radially expands into annular space V.

While the flow of a single sound wave of the propagating gas stream from chamber 3 tochambers 5 and 7 may be considered instantaneous yet the period is actually divided into a plurality of lagging time steps. During the time lag of passage of a wave from chamber 3 to second chamber 5 a part of a given wave has been intercepted by the barrier area 4 and has been discharged through expansion space V to the low (atmospheric) pressure in shell I2 and thence to the atmosphere. Immediately following this the concentric, tubular stream fraction or wave part S is arrested by the wall barrier area 6* and is radially expanded through space V to the shell l2 and to atmosphere. Finally, the core or center stream fraction S is stopped by baflle 9 and is radially expanded through space V and ports H] to the atmospheric shell l2.

Thus the full sound wave force is not thrown onto the atmosphere at one instant but is divided and discharged as time lagging fractions one after the other and their sound and vibration effects greatly choked.

The device has no closed, cushion forming chambers; no continuous line of fiow, direct or circuitous from end to end through which the wave propagating fluid must pass, and has no gradually-seaping, uninterrupted stream of gas flow. On the contrary, there is a positive stopping of numerous, contiguous, concentric fractions of the wave forming stream by the axially spaced, concentrically presented barrier areas 4 5 and baffle face 9. The stopped wave portions are outwardly, radially expanded in lagging time steps and impact the atmosphere in successive, weakened impulses.

What is claimed is:

' A sound wave sub-dividing device including an exhaust shell, and a series of progressively stepped-down chambers in the shell, one end of the shell being closed by a head to which the near end of the largest chamber is abutted concentrically of the shell, a gas conduit leading into said largest chamber through an axial inflow opening which is materially smaller than the diameter of said chamber, a first discal wall closing the back end of said chamber and having a first concentric, gas outlet which is materially smaller than the said inflow opening and said first wall constituting a baffle in front of which an annular volume of incoming gas is arrested and is permitted to unobstructedly expand toward and for the full length of said largest chamber; a second expansion chamber whose forward end concentrically abuts said first wall and is of materially larger diameter than the outlet in the first wall so as to provide for free direct outward expansion of gas coming through said wall, a second discal wall closing the back end of the second chamber and having a second, concentric gas outlet which is of materially smaller diameter than the first wall outlet and said second wall constituting a bafiie in front of which the incoming gas is arrested except at the second outlet and is permitted to expand unobstructedly toward and for the full length of the second chamber; and a third chamber concentrically abutting the second wall and being of materially larger diameter than the second wall opening and forming for its full length an unobstructed expansion space for the stream of gas incoming from the second wall opening; all of the said chambers having outlets into the exhaust shell.

HOWARD MCCURDY. 

